1. Field of the Invention
Lubricating and functional fluids manufacturers are under constant pressure to improve their products in response to manufacturers' and user demands. For instance, General Motors recently released its DEXRON.RTM.-III specification, which requires fluids with improved friction performance and thermal stability. Major properties of fluids subject to improvement pressure are chemical and thermal stability which in turn leads to improved anti-oxidation and long term lubricating and functional properties. While solving a given set of problems in fluids, care must be taken to also improve or at least retain other properties or operating parameters of the fluid. An example of this is to formulate lubricating fluids with improved or at least comparable anti-oxidation properties while retaining or improving functional properties imparted by the lubricating fluid while in use. The present invention deals with fluids whose functional properties have been improved by the addition of an additive package containing bis(alkylthioalkyl) ethers to the basic lubricating fluid to form a lubricating composition.
2. Description of the Art
Bis(alkylthioalkyl) ethers are known in the art. Their synthesis from 2-thioalkylethanols has been disclosed in U.S. Pat. No. 2,653,978 to Monsanto. Fokin et al in Bull. Acad. Sci U. S. S. R., Div. Chem. Sci. pp. 1667-1672 (1982) has also reported the self condensation products of alkyl substituted 2-thio ethanols to form the corresponding bis(alkylthioalkyl) ethers. The thio analog bis(alkylthioethyl) sulfide has been reported in Japanese patent 6,926,196 to Mitsubishi Rayon (CA 72, 79858d 1970). The above cited references reported the dodecyl compounds. All sulfur analogs have also been described and their use in lubricants reported in U.S. Pat. No. 2,230,966 to Socony-Vacuum Oil Company.
Condensation reactions of 2-hydroxyethyl sulfides with alcohols and phenols to yield the corresponding bis-(2-alkoxyethyl)sulfide and their use as lubricants has been reported by Richter et al in U.S. Pat. No. 2,582,605 to Socony-Vacuum Oil Company and by Richter et al in Journal of Polymer Science 74, 4076-4079, (1952). Woodward in Journal of Polymer Science, XLI, 219-223 (1959) reported on the autocondensation of thiodiglycol to give unspecified products. Andrews et al reported on the condensation of aliphatic hydroxy compounds with thiodiglycols in Journal of Polymer Science, XLI, 231-239 (1959).
Solomon, in U.S. Pat. Nos. 4,769,164 and 5,037,569 has synthesized anti-oxidant products for inclusion in functional fluids. The anti-oxidants are produced from condensation reactions of thiodialkanols with monohydric alcohols and hindered phenols. These sulfur containing products are of general formula ROCH.sub.2 CH.sub.2 SCH.sub.2 CH.sub.2 OR. In U.S. Pat. Nos. 4,764,299, 4,894,174 and 5,051,198 the reaction products of thiodiglycols with mercaptans are disclosed. In one embodiment the reaction products have formula RSASASR where A is alkylene and a composition which is the reaction products of a beta-thiodialkanol and a mercaptan.
U.S. Pat. No. 5,053,152 discloses dispersants for use in lubricant and fuel compositions obtained by condensing a hydroxyalkyl or hydroxyaryl compounds with amines. These dispersants are produced by the acid catalyzed condensation of the amine reactant with the hydroxy reactant. The reference indicates that the examples disclose the preparation of dispersants with high TBN (total base number) values in the range of 75-85. The reference also indicates that lubricants and functional fluids (e.g., automatic transmission fluids) containing these dispersants can also include zinc dialkyl phosphorodithioates.
U.S. Pat. No. 4,584,115 discloses that reaction products of boric acid or boron trioxide with epoxides having at least 8 carbon atoms are useful antiwear, friction-modifying and rest-inhibiting additives for lubricants. U.S. Pat. Nos. 4,455,243 and 4,495,088 disclose lubricating oils containing borated partial fatty acid esters of glycerol.
The use of phosphorus containing amides as antiwear agents for use in lubricant compositions is disclosed in U.S. Pat. Nos. 4,032,461; 4,208,357; 4,282,171; and 4,670,169. Phosphorus-containing esters useful as antiwear agents in lubricating compositions are disclosed in U.S. Pat. No. 3,359,203. The use of such esters as E.P. agents in lubricant compositions is disclosed in U.K Patent 1,347,845. WO 88/05810 discloses gear oil compositions which contain hydrocarbyl phosphite esters where the hydrocarbyl groups have 1 to 30 carbon atoms.
U.S. Pat. No. 4,758,362 discloses thiocarbamate additives for use in low phosphorus or phosphorus-free lubricating compositions. The additive has the formula ##STR1## wherein X is O or S, and Z is one of several listed groups. The reference indicates that these additives impart improved extreme-pressure and antiwear properties to lubricant compositions.
U.S. Pat. No. 3,702,300 discloses carboxy-containing interpolymers in which some of the carboxy groups are esterified and the remaining carboxy groups are neutralized by reaction with a polyamine having one primary or secondary amino group. These interpolymers are described as being useful as additives for use in lubricating compositions and fuels.
The present invention describes and claims compositions containing reaction products which are alkylthio derivatives of alkyl ethers which when incorporated in functional fluids or lubricating base fluids result in fluid composition having superior frictional and anti-oxidation properties. The above references are herein incorporated by reference for any portion pertinent to this invention.